Structural, chemical and tribo-mechanical surface features of Ti and nitrided Ti submitted to hydrogen low energy implantation

Hydrogen diffusion is a well-known cause of embrittlement in titanium devices, however the use of H-implantation has been investigated to enhance the titanium biocompatibility and bioactivity. In the present study, effects of the hydrogen ion implantation on Ti and nitrided Ti through glow discharge are reported, focusing the surface tribo-mechanical response at nanoscale. The structural and chemical features were also evaluated, before and after the hydrogen implantation, by NRA, XRD, XPS, SEM and EDS. The hydrogen implantation increased the H content on Ti up to two times, promoted the formation of δ-TiH precipitates and changed the Ti oxidation state, without affecting hardness and elastic modulus. Hydrogen implanted after nitriding produced blisters, formed by H accumulation near the surface region of the nitride layer due to its barrier effect. A “denitriding” process at very near surface region was also observed after the hydrogenation. Nitriding increased Ti hardness by 120% and elastic modulus by 18%. Hydrogenation became the nitrided Ti harder and stiffer, increasing the hardness and elastic modulus by 180% and 41%, respectively. In both Ti and nitrided Ti, nanotribological tests pointed out that the surface became brittle after hydrogenation. On the other hand, the H-implantation had negligible effects on the Ti and nitrided Ti tribological behaviors in the tests performed under severe dry conditions.